Camera systems are normally used within the security business for surveying a scene. The low cost of the cameras used and the simplicity involved for communicating with the cameras, typically over the Internet, provides for further possible applications such for example for use within a shop for determining a customer shopping behavior.
However, the collection of video data may unfortunately in some instances potentially compromise the privacy of anyone observed by the system. There is thus a trade-off between the advantages made possible with video analysis and the thereto related privacy issues. This is specifically apparent within an everyday situation where a person is typically not conscious of the fact that video capture is taking place, such as within the above mentioned shop, within a park, etc.
A solution to this problem is provided in U.S. Pat. No. 7,602,944, disclosing a computer-implemented method of identifying a moving object in a digital video stream of a scene. The identification of the moving object is achieved by threshold subtracting a current video frame from a short term average video frame. The video frame is typically of an in comparison low resolution, i.e. reduced resolution, whereby generally all details will be discarded and the privacy for e.g. the person(s) captured by the video camera is upheld. The objects detected within the scene may be “followed” through a plurality of subsequent video frames, allowing the direction of the object to be determined as well as for determining the number of objects passing into and out from a defined zone within the scene.
Even though the disclosure of U.S. Pat. No. 7,602,944 provides some relief to the privacy issues discussed above, there will be problems as the robustness of the system, specifically in relation to scenes with varying illumination, such as for example in an outdoor scenario. Accordingly, there is a need for a more robust method for object detection within a scene, preferably also allowing for the possibility of extracting further information relating to the detected objects while still keeping the privacy at an in comparison high level.
Further attention is drawn to US20130182114. US20130182114 makes use of a video camera and a depth sensor for determining a real life height and width of an object. In an organized environment, such as within a retail space, the method disclosed in US20130182114 may be used for object separation and subsequent tracking of the objects.
In addition, CN101388145 provides an automatic warning method for improving road safety. The disclosed method uses single camera “two-dimensional” object motion detection, including determination of a size and a speed of the object.